Method for preventing the discoloration of dihydric phenols

Abstract

Dihydric phenol is effectively prevented from discoloration by mixing the dihydric phenol with 0.00001 to 0.1% by weight of hydrocarboxylic acid on the basis of the dihydric phenol.

What is claimed is: 
     
       1. A method of substantially preventing discoloration of a dihydric phenol represented by the general formula, ##STR2## wherein R is a hydrogen atom or an alkyl group having 1-6 carbon atoms, comprising mixing the dihydric phenol with a hydroxycarboxylic acid in an amount of 0.00001 to 0.1% by weight based on the weight of the dihydric phenol, said acid being selected from the group consisting of tartaric acid, malic acid, lactic acid, tartronic acid and esters of said acids. 
     
     
       2. The method according to claim 1, wherein the hydroxycarboxylic acid is at least one member selected from tartaric acid, tartronic acid and esters thereof. 
     
     
       3. The method according to claim 1, wherein the mixing is effected at a temperature higher than the melting point of the dihydric phenol. 
     
     
       4. The method according to claim 3, wherein the mixing is effected under atmospheric or a reduced pressure. 
     
     
       5. The method according to claim 1, wherein the mixing is effected in an aqueous medium. 
     
     
       6. A dihydric phenol substantially prevented from discoloration by the method of claim 1. 
     
     
       7. The method of claim 1, wherein said phenol is resorcinol.